1. Field of the Disclosure
The present disclosure relates to the immobilizing of a housing holding a drive source, such as a polygon motor, installed in, for example, an image forming apparatus.
2. Description of Related Art
A housing supporting a motor that rotates at high speeds may be attached to a frame. For instance, in an image forming apparatus, a polygon motor that causes a polygonal mirror to rotate at high speeds of tens of thousands of rotations per minute may be mounted on an exposure device. The exposure device may be called a laser scanner unit (LSU). An exposure device of this kind reflects laser light off of a polygonal mirror, and scans and exposes a photosensitive drum to light in order to form a latent electrostatic image. A housing of an exposure device configured as a single unit is attached to a frame within the image forming apparatus. For instance, a technique such as that described below is known in relation to the attachment and positioning of an exposure device.
Specifically, there is known an image forming apparatus that includes an image support and a light scanner unit that exposes the surface of the image support to light and forms a latent electrostatic image, wherein the light scanner unit has an optical component for exposing the surface of the image support to light and a substrate upon which the optical component is provided; the light scanner unit is capable of rotating around an axis constituted by a supporting member attached to the frame of the image forming apparatus and extending through the substrate in the primary exposure scanning direction; the light scanner unit is supported so that movement in the primary scanning direction is prevented; and the light scanner unit is supported at a first support in the vicinity of one end of the supporting member, a second support in the vicinity of another end of the supporting member, and a third support that checks the rotation of the light scanner unit. This configuration is meant to prevent deformation of the light scanner unit while supporting and positioning same, maintaining high optical performance.
A motor (drive source), such as a polygon motor, that rotates at high speed possesses high levels of energy, which leads to vibration. The greater the amplitude of this vibration generated by the drive source becomes due to resonance, the greater the lens or polygonal mirror vibrates. The vibration can become great enough to shift the position on the photosensitive drum being irradiated with laser light, negatively affecting the quality of the formed image.
The same type of exposure device may be commonly installed in a plurality of models of image forming apparatus. The rotational speed of a motor such as the polygon motor is not always identical for each model of image forming apparatus. The rotational speed of the motor often varies according to the specifications of the various models of image forming apparatus. Generally, the greater the number of sheets printed per unit of time by a model, the higher the speed at which the polygon motor rotates. In inexpensive models, from which the same number of sheets printed per unit of time as that yielded by more expensive models is not expected, the rotational speed of the polygon motor is lower than that of more expensive models.
In this way, the rotational speed of the motor of an image forming apparatus varies from model to model, even when the same type of exposure device is installed. For this reason, the frequency of the vibration appearing in the housing of the exposure device varies from model to model due to the difference in motor rotational speeds. The housing is immobilized in place by a fastener or the like, reducing vibration to a certain degree. However, it may not be possible to completely eliminate the vibration generated by the motor depending on the positional relationship between the fastener site and the drive source, the shape and/or material of the housing, and the frequency of the vibration. For this reason, while the specifications (motor rotational speed) of some models might cause no problem with vibration, in the specifications of other models, vibration may be generated to such an extent that the image may be affected (i.e., beyond an acceptable degree) unless the vibration is stopped.
When vibration occurs beyond an acceptable degree, a preventative measure of adding a vibration damping member to the lens, mirror, and other members within the exposure device has conventionally been adopted in order to suppress vibration. The vibration damping member might be, for example, a weight, a plate (metal plate), a damping sheet (soft sheet) that cancels out vibration by converting the vibration to heat, or the like. However, the addition of a vibration damping member has presented the problem of increasing manufacturing costs through the cost of the vibration damping member itself and/or an increase in man-hours.
Also, the image forming apparatus described above does not provide against vibrations caused by a motor such as a polygon motor. For this reason, a problem has been presented in that vibration increases depending on the rotational speed of the polygon motor.